The present invention pertains to a timekeeping system commonly used in schools, hospitals, offices and industrial applications.
Many timekeeping systems are comprised of a master clock driving one or more “slave” or secondary clocks that are periodically updated to be time synchronous to the master. Older systems did not have the benefit of microprocessor technology, as do units produced today. In modern systems, both the master and secondary clocks frequently contain microprocessors, and it is advantageous to utilize this intelligence when performing installation and time correction. Secondary clocks in these systems may have either the traditional analog face or a digital display, or both.
Normally, timekeeping systems have several protocols, such as sync-wire 59 minute correction, sync-wire 58 minute correction, sync-wire National Time and Rauland correction, 2-wire digital communication, 3-wire digital communication, RS-485, and others. Currently, there are upwards of 40 or 50 different protocols in use around the world. Some are quite common whereas others are rarely used. These protocols frequently operate sending one or more voltage pulses from the master clock to the secondary clocks or sending data transmission from the master clock to the secondary clock. Depending on the protocol, the pulses vary in signal timing, such as pulse width, repetition rate, etc., that add complication when the system is first installed or new secondary clocks are later added to the system. Each secondary clock is capable of several protocols that must be set correctly at the time of installation.
Currently during system installation and correction, there are no tools available that automatically detect and select the correct protocol at the secondary clocks. In Blount et al. U.S. Pat. No. 6,205,090, there is disclosed an adjustable master/slave clock system having a time keeping correction apparatus that may be used to select among several time keeping correcting schemes, such as a 59th minute correction scheme, a 58th minute correction scheme and a National Time correction scheme. The correction scheme is not, however, automatically detected or selected by the clock system itself. Rather, the particular scheme desired must be manually selected by a user, such as with a switch. This is a time-consuming and error-prone chore for the user, particularly if numerous secondary clocks, each based on a different protocol, are added to the system after initial installation.